https://bugzilla.redhat.com/show_bug.cgi?id=1447517
--- Comment #17 from sanford rockowitz rockowitz@minsoft.com --- Re not installing a udev rule, unfortunately there is no single right thing to do. There may already be rules in /etc/udev/rules.d that affect the /dev/i2c devices (not all of which are necessarily for displays), and ddcutil should not stomp over them. See http://www.ddcutil.com/i2c_permissions/ for a discussion. A sample rules file is distributed in the package, and it is left to the user to modify and install the file as necessary. Not great, but it's the best I felt I could do without being the proverbial bull in the china shop.
If a rule affecting all /dev/i2c devices is to be installed automatically, it seems to me it would be more appropriately located in package i2c-tools.
Note that command "ddcutil environment" examines the system environment, particularly in regards to permissions, and suggests to the user what changes they need to make to their environment.